Similar packages:

Iceweasel/Firefox extension that enables customization of webpages with user scripts

Greasemonkey allows users of the Iceweasel/Firefox web browser to create or
download user scripts which modify the content or behavior of web sites. It
provides a powerful way to personalize the web. The scripts are written in
JavaScript and have access to many of Iceweasel's/Firefox's features.

A large collection of prewritten scripts can be found at userscripts.org